Imagine if you will a 12'x12' raised slab that houses a vertical propane tank and dispensing pump. This is outdoors. The slab sits approximately 10-12 ft from the building. The customer has previously installed 3/4" PVC Sched. 80 running in a trench from building to slab. I am trying to determine if this is acceptable. Obviously we have to change to rigid but I am unsure of any portion of this can be in PVC. I guess more specifically I am trying to find out what defines the boundary of the hazardous area? I have been pouring through Art. 500 and can't seem to find it. Open for guidance. Thank you.